Life as a Physicist

Fizzle! August 4, 2009

The biggest, most expensive physics machine in the world is riddled with thousands of bad electrical connections.

Ouch.

So starts a mostly accurate article in the New York Times about the current state of the LHC. There is good news and bad news in this sentence. To paraphrase a famous politician currently sight-seeing north of South Korea, it really depends on your definition of the word bad. To most people, if someone says that the electrical connection between your light and the wall socket is bad, then that means your light won’t work. That is the normal definition of bad. We High Energy Physicists have a different definition of bad. 🙂

For us, bad means that the connection isn’t going to conduct as much current as it could (I had a blog post about this a while back – but this article contains an excellent explanation – well worth registering if you have to to read it). And this is the reason behind the timing of this article. As I mentioned in that article it would not be until the beginning of August that the LHC group of scientists would have finished measuring all those connections – all those splices – and know exactly how bad they were. Tomorrow the LHC and CERN will announce exactly what energy they will run the LHC at initially.

But scientists say it could be years, if ever, before the collider runs at full strength, stretching out the time it should take to achieve the collider’s main goals…

And that is the bad part of the news. The bad connections mean that we can’t run at the full 14 TeV energy – we will run something short of that (I’m betting it will be 7.5 TeV – if I get it right it isn’t because I have inside information from the accelerator group!). The article is correct that running at this reduced energy won’t give us the access to the science we’d all expected and hoped for if we were running at 14 TeV.

But another thing to keep in mind is: we need data. Any data. And not to discover something new – because we need to tune up and commission our detectors! We’ve never run these things in anything but a simulated collider environment or looking for cosmic rays. We would probably be able to keep ourselves busy for almost a year with two months of data.

Indeed, these are birthing problems – no one has ever run a machine like this before. Which brings me to the one spot in the article that got my hackles up:

“I’ve waited 15 years,” said Nima Arkani-Hamed, a leading particle theorist at the Institute for Advanced Study in Princeton. “I want it to get up running. We can’t tolerate another disaster. It has to run smoothly from now.”

Nima, whom I also know (and like), is a theorist. If an experimentalist said this we would all make them run outside turn around three times, and spit to the north to cancel the jinx they would have just placed on the machine. I think we can all guarantee that there are going to be other failures and problems that occur. We hope none of them are as bad as this last one. But if they are, we will do exactly what we’ve done up to now: pick up the bits, study them, figure out exactly what we did wrong, and then fix it better than it was originally made, and try again.

There was one last quote in that article I would have liked to have seen more of a back story to:

Some physicists are deserting the European project, at least temporarily, to work at a smaller, rival machine across the ocean.

The story behind this is fascinating because it is where science meets humanity. The machine across the ocean is the Tevatron at Fermilab (I’m on one of the experiments there, DZERO). There is plenty of science still there, and the race for the Higgs is very much alive – more so with each delay in the LHC. So scientifically it is attractive. But, there is also the fact that a graduate student in the USA must use real data in their thesis. Thus the delays in the LHC mean that it will take longer and longer for the graduate students to graduate. In the ATLAS LHC experiment the canonical number of graduate students quoted I hear is about 800. Think of that – 800 Ph.D.’s all getting ready to graduate – about 1/3rd or more of them waiting for the first data (talk about a “big bang”). Unfortunately, you can’t be a graduate student forever – so at some point the LHC is taking long enough and you have to move back to the USA in order to get a timely thesis. Similar pressures exist for post-docs and professors trying to get tenure.

UPDATE: Just announced earlier today: they will start with 3.5×3.5 – that is, 7 TeV center of mass. This is exactly half the design energy of the LHC. The hope is that if all runs well at that energy they can slowly ramp up to 4×5 or 8 TeV. At 8 things start to get interesting as a decent amount of data at 8 will provide access to things that the Fermilab Tevatron can’t. Fingers crossed all goes well!

Actually the NYT reporter could had found a better simil. We all have lived in houses where it was no possible to switch fridge, TV set, HiFI, oven and air all at the same time. Furthermore, we all have had a plug where the jumper was not able to support all the electrodomestics plugged in it. And some of all even had appreciated how even when the jumper was (as it should not be!) strong enough, the plug was obviously taking heat.